If he threatened to taze you, you still have the right to kill him to defend yourself. If he said he was going to taze you, he should probably taze you - he should have threatened you with 'force' in the first place, rather than specifically a tazer/'non lethal force' as it allows him to use...
Cba to keep this running on forever, give me a price now and I can confirm/deny whether or not its enough (last time it sold for £17m which was probably way overpriced but whatever)